Proeuphractus Ameghino
Proeuphractus Amegh., 1886, Bol. Acad. Nac. Cienc. Cordoba, t. 9, p. 208.
This genus is seldom found, but is distinguished by Ameghino by the absence of a pelvic buckler, all the plates of the carapace being movable. From the Deseado beds, Ameghino describes two species, P. setiger and P. laevis, both based on isolated plates; the former distinguished by having no piliferous perforation in the furrows surrounding the central figure, and with well-developed pits on the posterior margin; while the latter has small piliferous perforations in the furrows and only rudimentary ones on the posterior margin. These features do not seem to me to distinguish species.
In addition to the foregoing, Ameghino has made a series of genera and species,[23] Archaeutatus, Amblytatus, Isutaetus, Sadypus, Hemiutaetus, Anutaetus, all based on isolated plates, and distinguished by variations in the central figure and the piliferous pits. I am unable to find a satisfactory basis for distinguishing the genera or species, and feel that, until more complete material is known, it is impossible to say which are valid genera or species.
Peltephilus Ameghino
- Peltephilus Amegh., 1887, Bol. Mus. La Plata, t. 1, p. 25 of separate.
- Cochlops Amegh., in part, 1889, Act. Acad. Nac. Cienc. Cordoba, t. 5, p. 792.
- Gephyranodon Amegh., 1891, Revista Argen., Hist. Nat., t. 1, p. 119.
- ? Anatiosodon Amegh., 1891, Revista Argen. Hist. Nat., t. 1, p. 327.
- Peltephilus Scott, 1903-5, Princeton Patagonian Exped., vol. 5, p. 88.
While rare, this genus is well known from the Santa Cruz, and is characterized by the curious development of the head shield, which consists of nineteen or twenty-one definitely arranged head plates, the anterior ones being developed into horn-like projections. The plates of the carapace are wide, thin, and unique in each having two to four wide shallow pits on the exposed surface. We found the genus rare, only two isolated plates turning up. From the Deseado material Ameghino has made three species: P. protervus, of very large size; P. undulatus, of moderate size, with the median figure accentuated and ending in two pits and with piliferous depressions on the margin; and P. depressus, of the same size as the foregoing, with a faint central figure, often four pits on the exposed surface and no piliferous pits on the margin. We found but one species, one plate of which combines characters of both the last two as described, so that I feel that there should be but two species, P. protervus and P. undulatus.
Peltephilus undulatus Ameghino
Fig. 133. Two movable
plates—natural size.